1. Field of the Invention
The present invention relates to an apparatus for adjusting the thickness of a resin printing plate within a given range. More particularly, the invention relates to an apparatus for forming a printing relief by molding a liquid photosensitive resin on a rigid base plate, adjusting the thickness of the resin, and then subjecting the relief to imagewise exposure.
2. Description of the Related Art
Heretofore, there have been known machines which adjust the thickness of a resin layer on a printing plate. One such machine incorporates the so-called spacer-laying method. One example thereof is shown in FIGS. 10A and 10B wherein spacers 102 and 102' are laid on opposite sides of rigid base plate 101. Liquid photosensitive resin feeding means 103 is moved along spacers 102 and 102', and liquid photosensitive resin 104 is fed onto rigid base plate 101 by actuation of liquid photosensitive resin feeding means 103 to form a resin layer having a predetermined thickness. The thickness of the resin layer is changed by interchanging the different size spacers 102 and 102' to adjust the height of the resin feeding means over the base plate.
A second type of machine incorporates the so-called elevation method which is disclosed, for example, in Japanese Patent Examined Publication No. 33061/80. In this method plate thickness is adjustable by a carriage provided with a resin feeding means which is movable upwardly and downwardly with reference to a rigid base plate. A third type of device incorporates the so-called molding base elevation method wherein a rigid base is provided so that it can be moved upwardly and downwardly on carriage rails relative to the resin carriage to adjust plate thickness.
However, there are drawbacks to the methods mentioned above. The spacer-laying method requires much time for replacing the spacers depending on the desired thickness of the resin plate. Furthermore, the spacers are long and relatively heavy and are difficult to handle. Further, it is necessary to maintain storage space for the different size spacers. Moreover, foreign materials are apt to stick to the spacers during the replacing operation, and if plate making is effected with the spacers having the foreign materials thereon, plate thickness becomes uneven.
The above mentioned elevation method requires a resin feeding means which is freely movable up and down. Therefore, the mechanism inevitably must be large, heavy, and very complicated. Thus, mechanical accuracy in the vertical movement of the feeding means is difficult to attain.
Furthermore, the molding base elevation method requires a mechanism for lifting and lowering a large and heavy rigid base plate while maintaining a high plane accuracy and parallel relation with the moving rails, and hence, the apparatus is largely overly complicated and expensive. Moreover, since the molding base plate is movable, it is difficult to maintain with repeated use and time the level of the molding base plate and the parallel relation of the base plate with the moving rails.
It is an object of the present invention to provide an apparatus for adjusting the thickness of resin plates which is free from the problems and/or defects in the conventional mechanisms and methods, and which provides a photosensitive resin plate superior in repetitive reproducibility and having a high degree of accuracy.
It is a further object of the present invention to provide a resin plate making machine capable of adjusting the thickness of the resin plate wherein the adjusting mechanism is compact, simple in construction, relatively light weight, and controllable from a remote station.